For a long time, the Ethernet has been widely applied due to cost efficiency. With the progress of time and technology, the Ethernet evolves to a 100G rate. Currently, the 100G Ethernet (100GE) is under standardization. The Institute of Electrical and Electronic Engineers Higher Speed Study Group (IEEE HSSG) has specified the requirements for the High Speed Ethernet (HSE) with a rate higher than 10G, and defines the subsequent standards to be formulated in view of the market potentiality, technical maturity, and cost efficiency. As limited by the technical difficulty and cost efficiency, the 100GE will evolve from multi-lane to single-lane in the future.
FIG. 1 shows a model of a multi-lane HSE. As shown in FIG. 1, the multi-lane HSE includes: a Media Access Control (MAC) module, adapted to generate MAC data; a Reconciliation Sublayer (RS) module, which is a lane between the MAC module and the physical-layer module; a Physical Binding Layer (PBL) module, adapted to distribute and converge multi-lane data; a Physical Coding Sublayer (PCS) module, adapted to encode the data from the MAC module; a Physical Medium Attachment (PMA) module, adapted to convert codes into bit streams suitable for being transmitted on the physical layer, and synchronize the data decoding; a Physical Medium-Dependent (PMD) module, adapted to transmit signals, amplify and modulate signals, and rectify waves; and a Medium-Dependent Interface (MDI), which defines the connector type corresponding to different physical media and PMD devices. The 100 Gigabit Medium-Independent Interface (CGMII) is a high-speed interface. Generally, based on the processing rate of the existing components, the possible bit width of the CGMII interface of the multi-lane 100GE is 640 bits or 320 bits.
The Ethernet physical-layer OAM overhead is adapted to provide the connectivity monitoring and fault management for the entire link of the Ethernet. The OAM overhead may be encapsulated in an Inter-Packet Gap (IPG) for transmission. The IPG is generated when the MAC sublayer sends MAC frame data. In the prior art, after the MAC sublayer sends a complete MAC frame, the MAC sublayer cannot send the next MAC frame before expiry of a gap required for sending 96 bits of data. The gap is called Inter-Frame Gap (IFG) on the MAC sublayer, and is called an IPG on the MII and the physical sublayer. Because the minimum IFG alone is defined, the period, in which no data is available for sending after a complete MAC frame is sent, is also regarded as an IFG and corresponds to the lower-layer IPG. The IPG reflects the data transmitted in the interval in which the physical layer stops sending the MAC frame data.
In the method for sending the OAM overhead in the prior art, if an OAM overhead needs to be sent while an MAC frame is being transmitted, it is necessary to wait until completion of sending the MAC frame, and then the OAM overhead is sent in the subsequent IPG. The detailed steps are described below:
Step 1: The data streams to be sent are sequentially received, and an IPG or a payload block in the data stream is sent in the time of every beat. The MAC data stream includes MAC frames and IPGs. As shown in 2a, the MAC frame is payload data in the data stream, and an MAC frame includes several payload blocks. For example, the first MAC frame includes a payload block a and a payload block b, and the second MAC frame includes a payload block c, a payload block d, and a payload block e. An IPG1 exists between the first MAC frame and the second MAC frame, namely, between the payload block b and the payload block c.
Step 2: MAC data streams are received sequentially. When the payload block b is received, a request for providing an IPG is received. The IPG is used to send an OAM overhead. As shown in FIG. 2b, a request for providing an IPG is received in the process of receiving the payload block b.
Step 3: The payload block a and the payload block b are sent, as shown in FIG. 2. In this step, no IPG is available for sending the OAM overhead, and it is necessary to wait to see whether the next beat is an IPG.
Step 4: The IPG1 after the payload block b is used to send the OAM overhead, as shown in FIG. 2d. 
Step 5: The subsequent payload blocks c, d, and e are sequentially sent, as shown in FIG. 2e. 
In the preceding process, after an IPG request is received, which requests for an IPG for sending the OAM overhead, it is necessary to wait for sending the OAM overhead. That is, the OAM overhead is sent by using the subsequent IPG only when the sending of the MAC frame is complete. This causes that the OAM overhead cannot be sent in time.